Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Equity securities | $ 800 | $ 751 |
| Common stocks | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Equity securities, at cost | 347 | 304 |
| Equity securities | 389 | 336 |
| Equity securities, fair value in excess of cost | 42 | 32 |
| Perpetual preferred stocks | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Equity securities, at cost | 388 | 380 |
| Equity securities | 411 | 415 |
| Equity securities, fair value in excess of cost | 23 | 35 |
| Equity securities | ||
| Debt and Equity Securities, FV-NI [Line Items] | ||
| Equity securities, at cost | 735 | 684 |
| Equity securities | 800 | 751 |
| Equity securities, fair value in excess of cost | $ 65 | $ 67 |